1. Field of the Invention
The present invention relates to an image forming apparatus, such as a copier, a printer, etc., and in particular, to a tandem type image forming apparatus including either a printing medium conveyance device that conveys a printing medium onto which plural toner image are directly transferred from image bearers or an intermediate transfer member that receives and transfers plural toner images transferred from the image bearers onto a printing medium at once. More particularly, the present invention relates to an image forming apparatus including a heat generating member and a heat transfer member inside the printing medium conveyance device or the intermediate transfer member.
2. Discussion of the Background Art
Conventionally, an image forming apparatus is equipped with a heating device that heats a transfer device to adjusts transfer environment and obtain a high quality image so that a transfer problem of a toner image can be resolved. For example, the Japanese Patent Application Laid Open No. 9-96971 discloses an image forming apparatus having a heat generating member that keeps temperature of a secondary transfer roller for the purpose of decreasing an environmental change of a resistance of a semi conductive secondary transfer roller within a prescribed ranged. Further, the Japanese Patent Application Laid Open No. 9-96971 controls temperature using a heat generating member that is controlled by a control device connected to a power supply of a separate lineage from a control system for a main apparatus, so that the power supply can be distributed to the heat generating member via the separated lineage and the temperature can be maintained even if a main power supply is turned off.
The Japanese Patent Application Laid Open No. 3-288174 discloses an image forming apparatus including a plate like heat generating member having a temperature self control function. Specifically, as mentioned above, the heat generating member is employed to decrease an environmental change of a resistance of a semi conductive secondary transfer roller within a prescribed range. In the image forming apparatus of the Japanese Patent Application Laid Open No. 3-288174, a thin cubic plate like heat generating member is cylindrically rolled up, and is inserted into the transfer roller. The Japanese Patent Registration No. 3,214,889 discloses an image forming apparatus that includes a heater arranged within a cleaning backup roller that internally contacts an intermediate transfer belt opposing a cleaning blade to remove toner remaining on the intermediate transfer belt. A heater is employed to maintain temperature of all of the intermediate transfer belt and the cleaning belt so that Young's modulus and flexibility of these devices and a fine cleaning performance can be maintained.
In the above-mentioned prior arts, plural members arranged either inside or outside the intermediate transfer member cause a problem in low temperature environment, thereby necessitating temperature keeping. Thus, they are each preferably provided with a heat generating member. However, numbers of the heat generating members increase cost. Further, since heat generating members which keep temperature of different members are closely arranged to each other, a space for the heat generating members becomes narrower. Otherwise, the image forming apparatus becomes bulky when the space is newly added. For the same reason, when a member is heated by a heat generating member that mainly heats a different member, temperature thereof excessively increases and causes heat interruption.